bzero in socket programming - c

Question

I am writing a simple client/server chat program in c. I am not understanding why one program works and the other doesn't. The programs given for client and server which are working are below. When I replace bzero(&(server.sin_zero),8) with bzero((char*)server,sizeof(server)) in both codes, it throws an error that "transport endpoint is not connected". They have implemneted using the second method and it works at this site.
Client.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
int main()
{
struct sockaddr_in server;
int s1;
char message[500];
server.sin_port = htons(5000);
server.sin_addr.s_addr = inet_addr("127.0.0.1");
server.sin_family = AF_INET;
bzero(&(server.sin_zero),8);
s1 = socket(AF_INET,SOCK_STREAM,0);
if(s1 == -1) {
perror("socket not created\n");
exit(1);
}
if(connect(s1,(struct sockaddr *)&server,sizeof(server)) == -1) {
perror("not able to connect\n");
exit(1);
}
int n = read(s1,message,500);
if(n < 0) {
perror("message not recieved\n");
exit(1);
}
printf("%s\n",message);
close(s1);
return 0;
}
Here is the program for the server.
Server.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
int main()
{
struct sockaddr_in server,client;
int s1,s2,len;
char message[500];
server.sin_port = htons(5000);
server.sin_addr.s_addr = INADDR_ANY;
server.sin_family = AF_INET;
bzero(&(server.sin_zero),8);
s1 = socket(AF_INET,SOCK_STREAM,0);
if(s1 == -1) {
perror("socket not created\n");
exit(1);
}
if(bind(s1,(struct sockaddr *)&server,sizeof(struct sockaddr)) == -1) {
perror("socket not binded\n");
exit(1);
}
if(listen(s1,5) == -1) {
perror("unable to listen");
exit(1);
}
len = sizeof(struct sockaddr_in);
s2 = accept(s1,(struct sockaddr *)&client,&len);
printf("connected");
if(s2 == -1) {
perror("unable to accept connection");
exit(1);
}
strcpy(message,"you are connected");
message[strlen(message)] = '\0';
int n = write(s2,message,strlen(message));
if(n < 0) {
perror("message not sent\n");
exit(1);
}
close(s1);
close(s2);
return 0;
}

Answer 1

bzero(&(server.sin_zero),8)
only zeroes out the sin_zero array.
bzero((char*)server,sizeof(server))
on the other hand, zeroes out the whole struct, thus resetting the values you set before (like sin_port).
Finally, first zero out the struct, then initialize it (just like they did it on the site you referred to; pay attention to the details :-)).